Normal Thyroid Test Result

Written by filonia lechat
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The thyroid, which affects many areas of the body, is an integral part of human anatomy. It is a gland that removes iodine from food and converts it into thyroid hormones. The thyroid affects many different areas of the human body—weight, mood, body temperature, hair consistency and loss, sexual function and skin consistency. While a person can function with lowered or heightened thyroid levels for a short period of time, it is important to address any problems quickly. Both men and women experience thyroid trouble, though women with thyroid problems outnumber men by quite a bit.

Two kinds of thyroid problems exist: hypothyroidism (sluggish or nonexistent thyroid functioning) and hyperthyroidism (an overactive thyroid). A few simple tests done by your doctor or endocrinologist will help determine whether you fall in the normal functioning range or require additional assistance for a thyroid problem.

T4 - Serum Thyroxine and Free Thyroxine

T4 is the main hormone produced by the thyroid. Your doctor will test your T4 levels with a simple blood test. Two versions of T4 provide insight into normal range: 4.6-12 ug/dl (micrograms per decilitre) is the normal range for serum thyroxine and 0.7-1.9 ng/dl (nanograms per decilitre) is the normal range for free thyroxine. In a person with hypothyroidism, their levels of the T4 range will be lower than average because the thyroid is not producing enough (or any) hormones. A hyperthyroidic person would be higher than average for these tests.

T3 - Serum Triiodothyronine and FT3I

A T3 test (also known as a free T3 index or FT3I) is often ordered by doctors after a T4 test comes back showing the patient is not in average range. Average range for T3 is 80 to 180 ng/dl.

TSH - Serum Thyrotropin

Thyroid stimulating hormone, also called thyrotropin or TSH, comes from the pituitary gland. It is the TSH that actually "instructs" the thyroid to secrete the T4 and T3 hormones. Testing TSH is the most important way of determining whether someone has a hypothyroid problem—if the TSH is malfunctioning, the T4 hormone will not receive the proper signals it requires.

An average TSH range is 0.5 to 6 U/ml (units per mililiter). In a hypothyroidic person, the levels will be higher than average. This is because when the thyroid is malfunctioning, the pituitary gland steps in and works into overdrive. A hyperthyroidic person's thyroid, on the other hand, will be working more than it should, and will override the pituitary gland (and the TSH); therefore, these patients would see lower than average numbers on this test.

Ancillary Tests

Other tests may also be ordered by your doctor. Their abbreviations and normal ranges are as following:

Free thyroxine fraction - FT4F - 0.03-0.005 per cent

Thyroid hormone binding ratio - THBR - 0.9-1.1

Radioactive iodine uptake - RAIU - 10-30 per cent

Serum thyroglobulin - Tg - 0-30 ng/ml (nanograms per mililiter)


Just as each human is different, thyroid numbers may differ, as well. This makes it extremely important to establish a good connection with your doctor or endocrinologist. It's also important to check in with yourself and see how you feel—you know yourself best. For example, if you notice that your tests are starting to fall off the normal range, but only slightly, it is still integral that you see a doctor to discuss them. Doctors can track you over time to create a healthy plan. Sometimes, a higher number on a test scale won't immediately require any kind of action, but your doctor will discuss this with you. Also note that some medications such as birth control and antibiotics can counter-indicate test results, so please let your doctor know anything you are taking. Keep in mind that the numbers here are the average, normal range for each test. Your own mileage will, of course, vary.

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